The great eruptions of the Icelandic Geysers are, it has been observed, accounted for by the siphon theory; in other words, this theory supposes the existence of a chamber in the heated earth, not quite full of water, and communicating with the upper air by means of a pipe, whose lower orifice is at the side of the cavern and below the surface of the water. The water, being kept boiling by the intense heat, generates steam, which soon accumulates such force as to discharge the contents of the pond into the air through the narrow vent, or, at least enough to allow of the escape of the superfluous steam. In the Great Geyser of Iceland this eruption occurs with tremendous power, lasting only a few moments, when, all the volume of water falling back into the pool, it sinks much below its ordinary level, and remains quiescent for several days, until a fresh creation of steam repeats the phenomenon.
'The Witches' Caldron,' which is the 'Great Geyser' of California, on the contrary, never rises into the air; the subterranean pond of which it is the safety valve, may be considered to rise in it, as in a pipe, to the surface. It is not necessary to suppose a siphon; a straight pipe, communicating with the air, will account for all that is peculiar to this hot spring.
Before attempting to describe the wonders of the 'Devil's Cañon,' it may be well to give some account of the Geysers of Iceland, to render this essential difference in character the more striking, especially as numerous theories, professing to account for the Californian phenomena, have been propounded by the people of that State, none of which are thoroughly satisfactory to any one who has examined them attentively.
The following is taken from 'Letters from High Latitudes,' which appeared in 1861, and is only one of many accounts by Iceland travellers. Those interested in these matters will derive much information from the sketches of Mr. J. Ross Browne, which have had many readers through Harper's Magazine. We quote:
'I do not know that I can give you a better notion of the appearance of the place than by saying that it looked as if for about a quarter of a mile the ground had been honey-combed by disease into numerous sores and orifices; not a blade of grass grew on its hot, inflamed surface, which consisted of unwholesome-looking, red, livid clay, or crumbled shreds and shards of slough-like incrustations. Naturally enough, our first impulse on dismounting was to scamper off to the Great Geyser. As it lay at the farthest end of the congeries of hot springs, in order to reach it we had to run the gauntlet of all the pools of boiling water and scalding quagmires of soft clay that intervened, and consequently arrived on the spot with our ankles nicely poulticed. But the occasion justified our eagerness.
'A smooth, silicious basin, seventy-two feet in diameter and four feet deep, wide at the bottom, as in washing basins on board a steamer, stood before us, brimful of water just upon the simmer; while up into the air above our heads rose a great column of vapor, looking as if it was going to turn into the Fisherman's Genie. The ground above the brim was composed of layers of incrusted silica like the outside of an oyster shell, sloping gently down on all sides from the edge of the basin.
'As the baggage train with our tents and beds had not yet arrived, we fully appreciated our luck in being treated to so dry a night; and having eaten everything we could lay hands on, we sat quietly down to chess, and coffee brewed in geyser water; when suddenly it seemed as if beneath our very feet a quantity of subterranean cannon were going off: the whole earth shook, and Sigurdr, starting to his feet, upset the chess board (I was just beginning to get the best of the game), and started off at full speed toward the great basin. By the time we reached its brim, however, the noise had ceased, and all we could see was a slight movement in the centre, as if an angel had passed by and troubled the water. Irritated by this false alarm, we determined to revenge ourselves by going and tormenting the Strokr.
'The Strokr—or the Churn—you must know, is an unfortunate geyser, with so little command over his temper and his stomach that you can get a rise out of him whenever you like. All that is necessary is to collect a quantity of sods, and throw them down his funnel. As he has no basin to protect him from these liberties, you can approach to the very edge of the pipe, about five feet in diameter, and look down at the boiling water, which is perpetually seething at the bottom. In a few minutes the dose of turf you have administered begins to disagree with him; he works himself up into an awful passion—tormented by the qualms of incipient sickness; he groans and hisses, and boils up and spits at you with malicious vehemence, until at last, with a roar of mingled pain and rage, he throws up into the air a column of water forty feet high, which carries with it all the sods that have been chucked in, and scatters them scalded and half digested at your feet. So irritated has the poor thing's stomach become by the discipline it has undergone, that long after all foreign matter has been thrown off, it goes on retching and spluttering, until, at last, nature is exhausted, when, sobbing and sighing to itself, it sinks back into the bottom of its den. Put into the highest spirits by the success of this performance, we turned to examine the remaining springs. I do not know, however, that any of the rest are worthy of any particular mention. They all resemble in character the two I have described, the only difference being that they are infinitely smaller, and of much less power and importance.
'As our principal object in coming so far was to see an eruption of the Great Geyser, it was of course necessary to wait his pleasure; in fact, our movements entirely depended upon his. For the next two or three days, therefore, like pilgrims round some ancient shrine, we patiently kept watch, but he scarcely deigned to vouchsafe us the slightest manifestation of his latent energies. Two or three times the cannonading we heard immediately after our arrival recommenced—and once an eruption to the height of about ten feet occurred; but so brief was its duration, that by the time we were on the spot, although the tent was not eighty yards distant, all was over; as after every effort of the fountain, the water in the basin mysteriously ebbed back into the funnel. This performance, though unsatisfactory in itself, gave us an opportunity of approaching the mouth of the pipe, and looking down its scalded gullet. In an hour afterward the basin was brimful as ever.
'On the morning of the fourth day a cry from the guides made us start to our feet, and with one common impulse rush toward the basin. The usual subterranean thunders had already commenced. A violent agitation was disturbing the centre of the pool. Suddenly a dome of water lifted itself up to the height of eight or ten feet—then burst and fell; immediately after which a shining liquid column, or rather sheaf of columns, wreathed in robes of vapor, sprang into the air, and in a succession of jerking leaps, each higher than the last, flung their silver crests against the sky. For a few minutes the fountain held its own, then all at once appeared to lose its ascending energy. The unstable waters faltered—drooped—fell, 'like a broken purpose,' back upon themselves, and were immediately sucked down into the recesses of their pipe.